Field monitoring of analog signals in a radar system

ABSTRACT

A FMCW radar system with a built-in self-test (BIST) system for monitoring includes a receiver, a transmitter, and a frequency synthesizer. A FMCW chirp timing engine controls timing of operations at least one radar component. The BIST system includes at least one switchable coupling for coupling a first plurality of different analog signals including from a first plurality of selected nodes in the receiver or transmitter that are all coupled to a second number of monitor analog-to-digital converters (ADCs). The second number is less than (&lt;) the first plurality of different analog signals. The BIST system includes a monitor timing engine and controller operating synchronously with the chirp timing engine, that includes a software configurable monitoring architecture for generating control signals including for selecting using the switchable coupling which analog signal to forward to the monitor ADC and when the monitor ADC samples the analog signals.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation and claims priority to U.S. patentapplication Ser. No. 15/333,593, filed Oct. 25, 2016, which is herebyincorporated herein by reference

FIELD

Disclosed embodiments relate to dynamic field monitoring of analogsignals in radar systems.

BACKGROUND

A conventional radar sensor unit (radar system) comprises a transceivercircuit having a transmitter including a waveform generator and ananalog front end (AFE) including an amplifier and a receiver thatincludes an AFE (amplifier, mixer, and filter) and an analog-to-digitalconverter (ADC). The radar system also includes a signal processingmodule/unit, such as a digital signal processor (DSP) or amicrocontroller unit (MCU). A radar chip may provide all thesecomponents, except perhaps the signal processing module/unit andantenna(s).

Data processing in a frequency-modulated continuous-wave (FMCW) radarsystem is performed on a system cycle/frame basis. A FMCW frame includesN (number) of FMCW ramps/chirps. A chirp is a smallest logical unit ofdata used for FMCW radar processing.

One application for such radar systems is for automotive collisionavoidance. In these radar systems, during field operation, the AFEcircuits need to be continually monitored to detect failures and/or toimprove their performance. In particular, preventing a malfunction inthe radar system can be important, and the ability to monitor a failureduring radar operation is a desirable feature. In order to satisfy suchrequirements, a built-in self-test (BIST) circuit or system may beincluded to test the transceiver circuit during radar system operation.

SUMMARY

This Summary briefly indicates the nature and substance of thisDisclosure. It is submitted with the understanding that it will not beused to interpret or limit the scope or meaning of the claims.

Disclosed embodiments recognize although BIST systems are known fortesting transceiver circuits of radar systems, such known BIST systemshave at least two limitations. Known BIST systems are generally nottime-aligned to the radar chirps of the radar system. This meanstransient failures/behaviors of signals which occur only during radarchirps, but not at other times, cannot be detected. Moreover, known BISTsystems do not provide instantaneous monitoring of multiple analogsignals in multiple system states through a common ADC.

Disclosed embodiments include methods and apparatus that monitor analogsignals in transceivers of radar systems to achieve dynamic RF and AFEcircuit monitoring for detecting failures and/or to improve radar systemperformance. A method of monitoring a radar system includes switchablycoupling a first plurality of different analog signals including from afirst plurality of selected nodes in a receiver or a transmitter of theradar system that are all coupled to a second number of monitor ADCs ofa built-in self-test (BIST) system. The second number is less than (<)the first plurality of different analog signals. A first of the firstplurality of different analog signals is selected to forward to themonitor ADCs. Samples output by the monitor ADC are processed forextracting statistics therefrom, and the selecting and processing arerepeated for at least a second of the different analog signals.Statistics are used for at least one of detecting a failure in (e.g.,through threshold comparison) and calibrating of the radar system (e.g.updating RF buffer bias settings to improve signal swing/signal to noiseratio (SNR)).

Another disclosed aspect comprises the monitoring the analog signalstime-aligned to functional radar chirps. Yet another disclosed aspectcomprises the instantaneous monitoring of multiple analog signals inmultiple system states through a number of ADCs that is less than lessthan the number of different analog signals, such as using only onesingle common monitor ADC for all the different analog signals in oneparticular embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, wherein:

FIG. 1 is a flow chart that shows steps in an example method ofmonitoring a FMCW radar system, according to an example embodiment.

FIG. 2A is block diagram of an example 1RX-1TX FMCW radar system thatincludes a disclosed BIST system which utilizes switches to providesreal-time monitoring or calibration including for the AFE circuitry.

FIG. 2B is block diagram of an example 1RX-1TX FMCW radar system thatincludes a disclosed BIST system which utilizes a multiplexer to providereal-time monitoring or calibration including for the AFE circuitry.

FIG. 3 shows a timeline for chirp aligned monitoring, according to anexample embodiment.

FIG. 4 shows a timeline for usage in inter-frame calibration/monitoring,according to an example embodiment.

FIG. 5 shows an example multiplexing and control scheme in analog.

FIG. 6 shows a BIST system having a digital hardware BIST FSMfunctioning as a monitor timing engine that implements time alignedmeasurement of analog signals from a radar system by working in tandemwith a FMCW chirping timing engine that it is synchronized with,according to an example embodiment.

DETAILED DESCRIPTION

Example embodiments are described with reference to the drawings,wherein like reference numerals are used to designate similar orequivalent elements. Illustrated ordering of acts or events should notbe considered as limiting, as some acts or events may occur in differentorder and/or concurrently with other acts or events. Furthermore, someillustrated acts or events may not be required to implement amethodology in accordance with this disclosure.

Also, the terms “coupled to” or “couples with” (and the like) as usedherein without further qualification are intended to describe either anindirect or direct electrical connection. Thus, if a first device“couples” to a second device, that connection can be through a directelectrical connection where there are only parasitics in the pathway, orthrough an indirect electrical connection via intervening itemsincluding other devices and connections. For indirect coupling, theintervening item generally does not modify the information of a signalbut may adjust its current level, voltage level, and/or power level.

FIG. 1 is a flow chart that shows steps in an example method 100 ofmonitoring a FMCW radar system, according to an example embodiment. Step101 comprises switchably coupling (e.g., by the multiplexer (MUX) 285shown in FIG. 2B below and/or by the switches (S1-S7) shown in FIG. 2Abelow) a first plurality of different analog signals including from afirst plurality of selected nodes in a receiver (Rx) or a transmitter(Tx) of the radar system that are all coupled to a second number ofcommon monitor ADCs of a BIST system. The second number is less than (<)the first plurality of different analog signals. The analog signals cancomprise, for example, common mode voltages of amplifier outputs,temperature sensor output voltages, RF signal swing sensor (powerdetector) output voltages, power supply circuits output voltages,synthesizer and phase locked loop (PLL)'s VCO control voltages. Theradar sub-systems can include Tx RF or IF, Rx RF or IF, powermanagement, synthesizer, or the PLL.

Step 102 comprises selecting (typically one at a time) a first of theplurality of different analog signals to forward to the monitor ADC(s).Step 103 comprises processing samples output by the monitor ADC(s) forextracting statistics (e.g., a minimum, maximum and average) therefrom,and repeating the selecting and processing for at least a second of theplurality of different analog signals. Step 104 comprises utilizing thestatistics for at least one of detecting a failure (e.g., through athreshold comparison) and calibrating the radar system (e.g., updatingRF buffer bias settings to improve signal swing/SNR). Method 100 canmonitor one hundred (100) or more critical signals in a typical FMCWradar system, including ten (10) or more signals during chirping.

FIG. 2A is block diagram of an example 1RX-1TX FMCW radar system 230that includes a disclosed BIST system 260 coupled thereto throughswitches shown as S1-S7 having a single monitor ADC 263. BIST system 260provides real-time monitoring or calibration for multiple analog signalswithin the FMCW radar system 230 that can be used to implement method100. Method 100 as noted above provides dynamic circuit monitoring todetect failures and/or to improve performance of the FMCW radar system230.

Although the FMCW radar system 230 is shown having only 1 Rx 210 and 1Tx 220, as known in the art of radar, there can be 2 or more of each ofthe Rx and Tx channels. FMCW radar system 230 includes an analog phaselock loop (APLL) 201 coupled to a FMCW synthesizer 205. The FMCWsynthesizer 205 includes phase frequency detector (PFD) and charge pump(CP) shown collectively as 205 a, a low pass filter (LPF) 205 b and avoltage controlled oscillator (VCO) 205 c in the forward path, and afrequency divider (DIV) 205 d in the reverse path. FMCW synthesizer 205is configured to generate a FMCW signal, which is a signal whosefrequency starts at a controllable frequency, and varies linearly withtime at a controllable rate or slope, for a controllable time duration.This operation of generating such an FMCW signal is simply calledfrequency ramping or “chirping”. FMCW synthesizer 205 is also shownincluding a FM-Sigma-Delta Modulator (SDM) block 205 e that is coupledto receive a timing control signal from the FMCW radar chirp timingengine shown as FMCW chirp timing engine 240.

Rx 210 is shown including a receive antenna 211. A low noise amplifier(LNA) 212 is shown driven by a low-dropout (LDO) regulator 213 which isa DC linear voltage regulator that can regulate the output. The outputof the LNA 212 is coupled to a mixer 214 having an output coupled to theinput of the band pass filter (BPF) 215. The mixer 214 receives the FMCWsignal from the FMCW synthesizer 205 after buffering by a buffer 232.Blocks 211-214, BPF 215 and bias generator 218 may all be considered theAFE of the Rx 210.

The mixer 214 down-converts the received RF signal. The output from theBPF 215 is coupled to an ADC 216. Although not shown, the output of theADC 216 may be coupled to a decimator (e.g., fast Fourier transform(FFT)-based for decimating down the radar signal to the requiredsampling rate) then to a buffer, then to a DMA coupled to a processor bya high speed interface (HSI) which can comprise low-voltage differentialsignaling (LVDS) or a camera serial interface (CSI), such as CSI-2. Theoutput of the processor can be coupled to the input of an engine controlunit (ECU) which may be provided to support an engine control functionincluding collision avoidance based on processing the radar data. In anengine control application, the processor processes the radar dataframe-by-frame to determine the range, velocity and angle of anyobstacle/vehicle in front of the radar system of the vehicle.

The Rx 210 is also shown including a power detector 217 coupled to aninput of the LNA 212 and a bias generator 218 coupled to an input of theBPF 215. The Tx 220 includes a transmitter antenna 221 and a phaseshifter 222 that is coupled to receive the FMCW signal from the FMCWsynthesizer 205 after buffering by the buffer 232. The output of thephase shifter 222 is coupled to a power amplifier (PA) 223 that isdriven by LDO 224, where the PA 223 drives the Tx antenna 221.

The FMCW chirp timing engine 240 controls the timing of the entire FMCWradar system 230. For example, it controls when the FMCW synthesizer 205should start ramping and stop ramping, when the T_(X) 220 and R_(X) 210should be enabled, when the ADC 216 samples should be collected forfurther processing to determine the presence and position of objectsaround the radar system. For this purpose, the FMCW chirp timing engine240 generates one or more timing control signals and provides them tovarious components of the radar system 230. One of the timing controlsignals is called “Chirp Start” that indicates the start of each chirpand may for example, control when then frequency ramping of each of theseveral chirps shown in FIG. 3 starts. Aligning the timing of monitoringof various analog signals in the FMCW radar system 230 at a controllabletiming offset from the chirp start signal is generally called chirpaligned monitoring herein and a software controllable architecture forchirp aligned monitoring is described herein.

FMCW radar system 230 is shown also including at least one temperature(Temp) sensor 233 that can be placed anywhere on the radar system chip,as well as a plurality of switches (S) coupled to various nodes shown asS1 to S7. FIG. 2A shows these switches comprising S₁ at the output nodeof the LDO regulator 213, S₂ at output node of the bias generator 218,S₃ to the output of the T sensor 233, S₄ to the output node of the powerdetector 217, S₅ to the output node of the LDO 224, S₆ to the outputnode of the power detector 225, and S₇ at the node between the LPF 205 band the VCO 205 c.

The FMCW radar system 230 (except in some embodiments the antennas 211,221) and BIST system 260 too can all be formed on a common substratethat has a semiconductor surface, such as a bulk silicon substrate or abulk silicon substrate having a silicon epitaxial layer thereon. FMCWradar system 230 can be realized as a complementary metal oxidesemiconductor (CMOS) chip formed on a semiconductor surface. Thesubstrate may also generally comprise other materials, such aselementary semiconductors besides silicon including germanium. Thesubstrate may also generally comprise a compound semiconductor material.

The BIST system 260 is shown including a monitor timing engine andcontroller 261 that is coupled to be synchronized with the FMCW chirptiming engine 240. A monitoring software block 262 pre-programs the listof signals to be monitored and their timing information into the monitortiming engine and controller 261, for example, which signals to monitor,their measurement order, settling time before measurement, and thenumber of samples to average. During the radar chirps for chirp-alignedradar system monitoring or inter-frame durations for inter-chirp radarsystem monitoring, the monitor timing engine and controller 261 forwardsappropriate nodes into the monitor ADC 263 at appropriate times, byenabling the appropriate buffers and switches (shown as S₁ to S₇) in themultiplexing path. Although not shown in FIG. 2A, the buffers in theFMCW radar system 230 function as repeaters that preserve at theiroutput the signals received at their input.

Buffers may be positioned at any or all of the dashed lines containingthe switches S1-S7 shown in FIG. 2A. Some buffers may act as repeatersthat preserve their input voltage information on their output voltage.Some buffers may act as current to voltage converters where their inputcurrent information is provided at their output voltage with a typicallyknown scaling resistance scale factor. Some buffers may act asprogrammable gain amplifiers which amplify the buffer input by a known(fixed or programmable) gain or factor forward to the monitor ADC 263.Buffers may also have a functionality of providing a high impedance atits output, such that its input is not forwarded to its output, based onthe buffers control signals. All these functionalities are collectivelyreferred to herein as being provided by buffers, and each buffer in adisclosed FMCW radar system may have one or more or none of thesefunctionalities.

The monitoring software block 262 collects statistics from thestatistics collector block 264 that are generated from outputs from themonitor ADC 263, such as minimum, maximum, average of various signals.These statistics can be used for failure detection (e.g., throughthreshold comparison) and/or calibrations performed by the calibrationsoftware block 265, such as updating RF buffer bias settings to improvethe signal swing or to improve the SNR.

FIG. 2B is block diagram of an example 1RX-1TX FMCW radar system 280that includes a disclosed BIST system 260′ which utilizes a MUX 285 toprovide real-time monitoring or calibration including for the AFEcircuitry. MUX 285 replaces the switches S1-S7 in FIG. 2A and has itsoutput coupled to the monitor ADC 263.

FIG. 3 shows an example timeline 300 for chirp-aligned FMCW radar systemmonitoring, according to an example embodiment. This example showsdisclosed FMCW radar system monitoring for frames that includeinterleaved short-range radar (SRR) chirps from 79 GHz to 81 GHz at 3dBm power and mid-range radar (MRR) chirps from 78.5 GHz to 79.5 GHz at13 dBm power. The monitor software block 262 (in FIGS. 2A and 2B)configures a signal list that provides a listing of the monitoredsignals and timing for the monitor timing engine and controller 261 (inFIGS. 2A and 2B) before the frame. A chirp is the transmission of theelectromagnetic wave whose frequency varies linearly, such as from 79GHz to 81 GHz in a duration of say, 100 μs. In FMCW radar, a frame mayrefer to a quick succession or series of chirps of one kind or manykinds. For example, a frame may contain 40 successive identical chirps,each of 100 μs duration and an inter-frame duration of say, 1 ms. Suchframes may get repeated multiple times in a typical radar operation.Chirps getting repeated in a frame may be identical or not. Framesgetting repeated in a radar operation may be identical or not. Themonitoring techniques described herein are applicable during theinter-frame times as well as during the chirps.

Since there may not be available sufficient time for software tointerfere and control the monitor ADC 263 for each parameter and betweenchirps, in disclosed embodiments the software programs, before the startof a frame provide the information needed for the monitoring timingengine and controller 261 to perform the required monitoring during thechirps and the frame. The information is basically an ordered list ofsignals to monitor during the subsequent frame of chirps, including anysettling time before measuring any parameter after each parameterchange, since many signals are measured one after another, and thenumber of time to sample for each measurement, just to improve the SNRin the measurement. The remainder of the intra-chirp/frame monitororchestration is generally performed autonomously by monitor timingengine and controller 261.

For example, during each radar frame, a monitor FSM which can realizethe BIST system 260 may maintain a running average, minimum, and maximumof FMCW radar system parameters including:

1. for FMCW Synthesizer 205 the VCO 205 c voltage at the chirp start(e.g. 0.1V);

2. for FMCW Synthesizer 205 the VCO 205 c voltage at the chirp end (e.g.0.9 V);

3. Tx 220 Power, Rx 210 Power (e.g. 10 dBm);

4. LNA 212 bias signals, and

5. Temperature from the temperature sensor 233.

6. Output common mode voltages of amplifiers such as LNA 212.

The FMCW radar system parameters 1-3 above can be used to determinewhether the VCO 205 c is operating out of range. Parameter 3-4 can beused to determine whether the radar system 230 is transmitting at asufficient level of power. These radar system parameters are maintainedfor each profile in the frame, with separate statistics over the framebeing generated for the SRR and the MRR chirps in this example. At theend of frame, the monitor software block 262 compares the statisticsobtained with stored allowed thresholds.

Regarding a “profile” as used herein, a frame as described above cancontain many identical or non-identical chirps. Each kind of chirp isone profile. A profile is a unique identification for TX outputpower=say 3 dBm, FMCW frequency range=79 GHz to 81 GHz, FMCW slope=2GHz/100 μs, chirp duration=100 μs, R_(X) LNA 212 gain=say 30 dB, RX BPF215 cutoff frequencies=say 500 KHz to 5 MHz. A profile is given a namesuch as SRR Profile (for the abovementioned profile) which can be seenin association with FIG. 3 which shows the time line of a framecontaining chirps of alternate SRR and MRR (Medium Range Radar)profiles. An MRR profile may be defined as TX output power=say 13 dBm,FMCW frequency range=78.5 GHz to 79.5 GHz, FMCW slope=1 GHz/130 μs,chirp duration=130 μs, RX LNA gain=say 40 dB, RX BPF cutofffrequencies=say 300 KHz to 7 MHz.

These profile details are given to the FMCW radar system 230 or 280including all the mm wave/analog components and FMCW timing engine. TheFMCW timing engine and controller 261 controls all the mm wave/analogand digital blocks based on the timing and other instructions which arepart of this profile definition. A frame, as describes above, maycontain many identical or non-identical chirps. A frame may also referto a set of chirps occurring between when monitoring software configuresvarious hardware components of the monitoring architecture and when itaccesses the results from the same.

FIG. 4 shows an example timeline 400 for usage in inter-frame FMCW radarsystem calibration or monitoring, according to an example embodiment.Example radar frames are shown being 10 ms long, with a 10 msecinter-frame time between the frames. In this embodiment, calibration ormonitoring is performed during the 10 msec inter-frame intervals. Thesignals shown (temperature, bias signals, common mode voltage, LO bufferpower) are measured and calibrated during inter-frame times or tomonitor to determine if bias signals and common mode voltages ofamplifier outputs are within allowed thresholds. An example list ofsignals that can be multiplexed to monitor can comprise the following:

Common mode voltages of amplifier outputs, temperature sensor 233 outputvoltages, RF signal swing sensor (power detector) output voltages, powersupply circuits (LDO) 224 output voltages, FMCW Synthesizer 205 and theAPLL's 201 VCO 205 c control voltages. These are nodes are in varioussub-systems in the FMCW radar system such as the Transmitter RF or IF,Receiver RF or IF, Power Management, Synthesizer, or APLL 201.

FIG. 5 shows an example multiplexing and control scheme 500 in analogfrom various subsystems of a FMCW radar system into a MUX 285 in serieswith an input of a single common monitor ADC 263 of a BIST system 260.Analog system 530 shown in FIG. 5 represents the analog, mm wave, andthe RF blocks shown as FMCW radar system 230 in in FIG. 2A and FMCWradar system 280 in FIG. 2B. RX CH 1-4 shown represents 4 identicalreceiver channels. Although not shown, there can be TX CH 1-4 whichrepresent 4 identical transmitter channels.

The block shown as CLK TOP represents an Analog Phase Lock Loop (APLL)and clock dividers and buffers system generating various clock signalsfor the various digital and analog sub systems in the radarsystem-on-a-chip (SoC). The block shown as REF SYS RX/TOP representspower supply, band gap and constant reference current and voltagegeneration circuits supplying them to various analog sub systems in theradar SoC. The block shown as LO TOP represents the local oscillatorsystem containing a FMCW Synthesizer, and buffers and multipliers anddividers on its output which generate the input signal to TX channelsand RX mixer components.

A one-hot encoded control signal (such as being 256 or 512 bits)generated by digital circuitry (such as the digital BIST FSM 600 shownin FIG. 6 described below) shown as block control (One-Hot) 520 is usedto select from the analog blocks in analog system 530 to be currentlyunder test. The broadcast generic control (generic control) signal shownas broadcast generic control 510 is changed to adjust the state of theradar system. Block control 520 is used to select the particular signalto be currently passed to the monitor ADC 263. Block control 520 andgeneric control 510 each represent digital signals generated by themonitor timing engine and controller 261 shown above in FIG. 2A and FIG.2B. In general, the block control 520 provides the digital controls thatcontrol the buffers, switches (S1-S7) of FIG. 2A or MUX 285 in FIG. 2Bwhich forward a desired analog signal to the monitor ADC 263 based onthe current block control signal. This select arrangement avoids theneed for complicated decoding logic inside the analog circuitry.

The broadcast generic control 510 (shown as 32 bits) is used toconfigure the internals of the selected analog block to adjust the stateof the FMCW radar system. Having a single broadcast generic control 510signal fanned out to all analog blocks under BIST simplifies the controlin digital. The one-hot encoded signals from the block control 520 canbe scattered and the generic control 510 can be duplicated multipletimes on the periphery of the analog to avoid long routes inside theanalog. A BIST FSM can provide the broadcast generic control 510 and theblock control 520, such as the BIST FSM 600 in FIG. 6 described below,where block control 520

As described above, the block control 520 basically controls whichparticular signal of which radar sub-system should get forwarded to themonitor ADC 263. One may want to further observe that signal undervarious states of operation of the radar SoC/analog, etc. The broadcastgeneric control 510 signal is used to enable the appropriate buffersand/or switches needed further to route the desired analog signal to themonitor ADC 263 and/or adjust the state and communicate that state. Thegeneric control 510 signal which is broadcast to all blocks isapplicable to a block of a radar sub-system only if the block controlhas enabled that block of that sub system.

In one example, to measure the TX output power through the TX powerdetector, the TX power amplifier output is forwarded to the monitor ADCby appropriately setting the block control 520. But the accuracy of theTX output power measurement may be improved by making two measurementsin quick succession—a) one with the TX power amplifier output connected,giving an ADC reading V1=P1+O1, where P1=Actual TX power and O1=unknownOffset and b) another with it disconnected from the monitor ADC, givingan ADC reading V2=O1 and using the difference, V2-V1, between the twomonitor ADC output readings to know the TX output power magnitude (P1)with greater accuracy than with only the a) part, due to O1 beingconstant or a relatively very slow varying noise. In this case, thegeneric control is first made to allow a) and then b) with a controlledtiming, without changing the Block control and hence without changingthe signal being forwarded to the monitor ADC.

In a radar system which has a large number of signals to monitor, thisconcept of block control 520 and broadcast generic control 510 allowsreduction in the number of bits to store in the instruction packet (see269 a in FIG. 6) for each measurement. This is in conjunction with thefact that the block control 520 is in one embodiment stored in theinstruction packet of 269 a in binary form (e.g. if there are 255signals to measure, use an 8 bit binary number to represent each signal)whereas, after a binary to one-hot conversion inside the monitor timingengine and controller 261, the block control 520 is passed in the formof a one-hot signal to the analog block, where only one signal in theone-hot block control is made one (others are zero) and it is directlyconnected in analog as e.g. the switch controls to all switches. Achange in the block control 520 may cause high number of glitches in themonitor ADC 263 input path during any signal transition but a change inthe generic control 520 may not cause such glitches and may be quicker.

In another embodiment/example the mux path for a particular signal beingforwarded to the monitor ADC 263 may contain voltage amplifiers ofprogrammable gains and the generic control may tell the desired gainduring the measurement while the block control may just tell whichsignal should be forwarded through this programmable gain block into themonitor AD 263. In another embodiment, the programmable gain block maynot be inside the MUX but be a part of one or more blocks in thesub-systems in the analog of FIG. 5 (same as FMCW radar system 280 shownin FIG. 2B).

The multiplexing scheme provided enables back-to-back instantaneousmonitoring of multiple analog signals through a common monitor ADC 263.In an example implementation, 200 or more analog signals from 10+ radarsub-systems are forwarded to the monitor ADC 263 in a softwareconfigurable manner. This can be accomplished by using the one-hotselect block control 520 shown as <N:0> to select a particularsub-system/node and an additional broadcast generic control 510 shown as<31:0> used to enable the appropriate buffers and/or switch the switchesneeded further to route the desired analog signal to the monitor ADC 263and/or change the state of the FMCW radar system.

FIG. 6 shows a BIST system 260″ having a digital hardware BIST FSM (BISTFSM) 600 functioning as a monitor timing engine and controller 261 thatimplements time-aligned measurement of analog signals 602 from a radarsystem by working in tandem with a FMCW chirping timing engine 240 thatit is synchronized with. The chirp start signal from the FMCW chirptiming engine 240 is provided to the BIST FSM 600 (see the “In-Sync”shown in FIGS. 2A and 2B). If desired, this arrangement enables the BISTFSM 600 to perform its functions time aligned to the chirp start signal,so that critical analog signals can be monitored when the functionalradar chirps are on-going, such as at controllable timing offsets fromthe start of the chirps.

Control signals shown as the block control 520 one hot and broadcastgeneric control are shown, which are generated by the BIST FSM 600 formultiplexing out signals from a selected analog block of the FMCW radarsystem under test using MUX 285 that has its output coupled to themonitor ADC 263. Precise control of the sampling window is provided formonitoring various signals in the radar system within any givenchirp/frame. The samples output by the monitor ADC 263 are coupled to amonitoring software block shown as skip/collect samples logic 262′, thento a statistics block shown as min/max/sum logic 264′ for signalprocessing to extract statistics such as minimum, maximum and average.This process is repeated for multiple analog signals.

Min/max/sum logic 264′ is shown outputting packets by “packet creation”which comprises generating independent Statistics Results Memory (SRM)(containing these statistics independently for various signals,independently for different profiles in the frame. The SRM is acollection of several memory elements which store the statistics ofvarious signals that are measured using the BIST system (independent foreach analog signal). The statistics contains, for example, minimum,maximum and average or sum of the monitor ADC outputs when measuring ananalog signal. The SRMs may be read by the monitoring software/firmwareand be utilized for a variety of purposes, such as for detecting afailure in (e.g., through threshold comparison) and/or calibrating theradar system. Sampling is generally enabled after allowing anappropriate settling time.

The skip/collect samples logic 262′ is generally implemented in adigital state machine hardware (HW) which skips the first N samplescollected from monitor ADC 263 (in a way of allowing settling time) andthen using the subsequent M samples for further processing. Similarly,the min/max/sum logic 264′ is also implemented inside digital HW. Thisis useful because a frame may for example have 256 chirps, each having 4signals to monitor, each with 2 samples skip and 3 samples to use. Insuch a case, instead of providing A) 4×256×(2+3) ADC readings to themonitoring software, one implementation has the HW provide to firmware(FW): B) only a summary: 4 min, 4 max, 4 sum quantities. These min, max,and sum are those corresponding to the minimum of all 3×256 readings ofeach signal and similarly max and sum. The skip samples are ignoreddirectly by the HW instead of forwarding to monitoring softwareneedlessly for SW to ignore. In other embodiments A) may be done, whilethe statistics collector 264 of FIG. 2A and FIG. 2B does the job of B.

There is also provided a provision for a full sequence of successiveanalog measurements to be executed. An instruction memory 269 coupled tothe BIST FSM 600 is shown receiving a chirp profile that stores all thechirp sequences needed by the BIST FSM 600 to generate the requiredcontrol signals for all chirp profiles in a frame for monitoring themultiple analog signals. An example FW instruction 269 a output by theinstruction memory is shown that is provided to the BIST FSM 600. Theinstruction memory 269 can be realized by FW run by a processor toconfigure the BIST FSM 600 to perform as needed and processing thestatistics of each analog signal to determine if the correspondingcircuit has failed (e.g. by comparing against known thresholds) or tofind optimum parameters for that circuit or other related circuits toimprove the radar system's performance.

In one implementation the monitoring software/firmware (such as monitorsoftware 262 in FIG. 2A and FIG. 2B) preprograms the instruction memory269, as a sequence of several instructions of the format shown as FWinstruction 269 a. The BIST FSM 600 (same as the monitoring timingengine and controller 261 shown in FIGS. 2A and 2B) waits for the chirpstart signal from the FMCW timing engine 240 and immediately afterreceiving it, reads the instruction sets such as FW instruction 269 aone by one. BIST FSM 600 forwards the block control 520 (after binary toone hot translation) and broadcast generic control 510 signals to theanalogic circuitry in the FMCW radar system. The BIST FSM 600 keepsthose controls in one state until the instructed number of “skipsamples” from monitor ADC 263 are skipped and “collect samples” numberis collected from it. The BIST FSM 600 also instructs the statisticscollector 264 of FIG. 2A and FIG. 2B at appropriate times to use themonitor ADC 263 outputs for the purpose of calculating min, max and sumstatistics and store in a “statistics results memory”. After the firstsignal indicated in FW instruction 269 a is “finished”, the BIST FSM 600next fetches the next instruction, say an instruction 269 b (not shown,but having similar format as 269 a and requesting a different analogsignal to be monitored) by having different block control 520 andbroadcast generic control 510 signals.

The FSM 600 does what was explained for FW instruction 269 a again for269 b (not shown) and stops after executing all entries of 269 (a, b, c. . . ) and starts waiting for the next chirp's “chirp Start” from theFMCW chirp timing engine 240 to indicate next chirp start. Uponreceiving that, it repeats the process, thereby updating the min, max,sum by reading the previous statistics from “statistics results memory”(SRM) accordingly. For example, if the current sample is lower than thatstored as the previous minimum in the SRM then it stores the currentsample as the min in the SRM. Similarly for max, where instead of lower,it is higher. Similarly for sum=current sample+sum present in SRM.Therefore, when the entire frame gets completed, the SRM contains themin., max., sum for all signals instructed through FW instruction 269 a,b, c, . . . in corresponding SRMs. the monitoring software can readthese SRMs and perform threshold comparisons and averaging etc. forfailure monitoring or calibration purposes.

It is noted for simplicity, the above explanation is for a framecontaining identical chirps where, the SRMs are maintained for differentsignals corresponding to FW instruction 269 a, b, c, etc. In a moresophisticated embodiment the instruction memory 269 as well as thecorresponding SRMs are maintained in a way to distinguish between theprofiles. For example, in FIG. 3, where SRR and MRR are alternated, say128 SRR profile chirps interleaved with 128 MRR profile chirps, the FWinstructions 269 a, b, and c, are present as one set for SRR profile andanother for MRR profile, and the corresponding SRMs too are keptseparate. This is because, otherwise the e.g. min statistic of TX powersignal/parameter may only store the min of SRR (near 3 dBm) because SRRTX power is programmed lower than MRR TX power by configuration andexpectation as per MRR and SRR profile definition as described aboveregarding the defining of profiles.

Therefore, at the end of the frame of FIG. 3, the monitoring software262 can read the SRMs of each signal/parameter of SRR and declare thatSRR operation had failed or passed based on threshold comparisons ofSRMs corresponding only to SRR and more importantly, also update theanalog configurations to be applied under SRR profile based on thecontents of SRMs of various signals. The monitoring SW can additionallydo this similarly and independently for MRR profiles. Note here that thestatistics collector 264 contains the SRMs corresponding to allprogrammed signals instructed by monitoring SW through FW instruction269 a, b and c (not shown) for SRR profiles and other instructions forMRR profiles too.

Advantages of disclosed embodiments include on-chip, quick and dynamicmonitoring of critical analog signals for radar systems, that can betime aligned to radar chirps. Time alignment ensures that transientfailures/behaviors of signals which occur during radar chirps, but notat other times, can be detected. For example, supply voltages dippingbelow limits only during radar chirps/frames due to peak powerconsumption, synthesizer control voltages exceeding valid limits onlyduring FMCW radar chirps, transmitter's output power which can be lowonly during radar chirps/frames, temperature behavior during radarchirps/frames only occur during radar chirps. Less additional time needsto be spent in monitoring these signals after radar chirps/frames, ifmonitoring is to be performed during radar chirps/frames, thusconserving power.

Those skilled in the art to which this disclosure relates willappreciate that many other embodiments and variations of embodiments arepossible within the scope of the claimed invention, and furtheradditions, deletions, substitutions and modifications may be made to thedescribed embodiments without departing from the scope of thisdisclosure.

What is claimed is:
 1. A method comprising: coupling, by a multiplexer,a first node and a second node in a frequency-modulated continuous-wave(FMCW) radar system to a built-in self-test (BIST) system based onsignal monitoring information; sampling, by the BIST system, a firstanalog signal from the first node and a second analog signal from thesecond node; calculating, by the BIST system, statistics from thesampled first analog signal and the sampled second analog signal; andupdating, by the BIST system, settings for the FMCW radar system basedon the calculated statistics.
 2. The method of claim 1, wherein thefirst node is coupled to a receiver of the FMCW radar system and thesecond node is coupled to a transmitter of the FMCW radar system.
 3. Themethod of claim 1, wherein the signal monitoring information comprisestiming information that causes the multiplexer to couple the first andsecond nodes during chirps performed by the FMCW radar system.
 4. Themethod of claim 1, wherein the signal monitoring information comprisestiming information that causes the multiplexer to couple the first andsecond nodes between chirps performed by the FMCW radar system.
 5. Themethod of claim 1, wherein the settings for the FMCW radar systemcomprise radio frequency (RF) buffer bias settings.
 6. A systemcomprising: a receiver including at least one amplifier and a mixer; atransmitter including a phase shifter and at least one amplifier, and afrequency synthesizer coupled to the mixer and coupled to the phaseshifter; a frequency-modulated continuous-wave (FMCW) chirp timingengine for controlling a timing of operations for the frequencysynthesizer; a multiplexer for coupling a first node and a second nodein a frequency-modulated continuous-wave (FMCW) radar system to ananalog-to-digital converter of a built-in self-test (BIST) system basedon signal monitoring information from the FMCW timing engine; and theBIST system configured to: sample a first analog signal from the firstnode and a second analog signal from the second node; calculatestatistics from the sampled first analog signal and the sampled secondanalog signal; and update settings for the FMCW radar system based onthe calculated statistics.
 7. The FMCW radar system of claim 6, whereinthe first node is coupled to the receiver of the FMCW radar system andthe second node is coupled to a transmitter of the FMCW radar system. 8.The FMCW radar system of claim 6, wherein the multiplexer couples thefirst and second nodes between chirps performed by the FMCW radar system9. A method comprising: initiating transmission of a first chirp of aframe of chirps by a frequency modulated continuous wave (FMCW) radarsystem comprising a first node and a second node; receiving a firstplurality of samples of a first signal from the first node and a secondplurality of samples of a second signal from the second node by abuilt-in self-test (BIST) system within a duration of the first chirp,wherein the receiving is performed responsive to a chirp start signalfor the first chirp; extracting, by the BIST system, statistics from thefirst plurality of samples and the second plurality of samples;initiating transmission of a second chirp of the frame of chirps by theFMCW radar system; receiving a third plurality of samples of a thirdsignal from the first node and a fourth plurality of samples of a fourthsignal from the second node by the BIST system within the duration ofthe second chirp, wherein the receiving is performed responsive to achirp start signal for the second chirp; and extracting, by the BISTsystem, statistics from the third plurality of samples and the fourthplurality of samples.
 10. The method of claim 9, further comprisingupdating, by the BIST system, settings in the FMCW radar system based onstatistics from one or more of the first, second, third, and fourthplurality of samples.
 11. The method of claim 9, wherein receivingfurther comprises coupling the first node and the second node to theBIST system in turn responsive to the chirp start signal for the firstchirp and the chip start signal for the second chirp.
 12. The method ofclaim 11, wherein the first node and the second node are coupled in turnto an analog-to-digital converter comprised in the BIST system.
 13. Themethod of claim 9, further comprising configuring the BIST system beforetransmission of the frame to sample signals from a sequence of nodesduring each chirp of multiple chirps of the frame during thetransmission, wherein the first node and the second node are comprisedin the sequence.
 14. The method of claim 9, further comprising:receiving a fifth plurality of samples of a fifth signal from a thirdnode comprised in the FMCW radar system and a sixth plurality of samplesof a sixth signal from a fourth node comprised in the FMCW radar systemby the BIST system within an inter-frame interval between end oftransmission of the frame and initiation of transmission of a next frameof chirps; and extracting, by the BIST system, statistics from the fifthplurality of samples and the sixth plurality of samples
 15. A frequencymodulated continuous wave (FMCW) radar system comprising: a chirp timingengine configured to control timing of operations for transmitting aframe of chirps; a plurality of nodes selectable to send respectivesignals to a built-in self-test (BIST) system during transmission of theframe of chirps; and the BIST system coupled to the chirp timing engineto receive chirp start signals for chirps in the frame, the BIST systemconfigured to: sample a signal from each node of selected nodes of theplurality of nodes during each chirp of a plurality of chirps of theframe responsive to receiving a chirp start signal for the chirp; andextract statistics from each sampled signal.
 16. The FMCW radar systemof claim 15, wherein the BIST system is further configured to sample asignal from each node of the selected nodes using a singleanalog-to-digital converter (ADC) that is coupled to each node of theselected nodes in turn during each chirp of the plurality of chirps. 17.The FMCW radar system of claim 15, wherein the plurality of nodes isalso selectable to send respective signals to the BIST system duringinter-frame intervals between transmissions of frames of chirps by theFMCW radar system and the BIST system is further configured to: sample asignal from each node of second selected nodes of the plurality of nodesduring at least one inter-frame interval; and extract statistics fromeach sampled signal from each node of the second selected nodes.
 18. TheFMCW radar system of claim 6, wherein the signal monitoring informationcomprises timing information that causes the multiplexer to couple thefirst and second nodes during chirps performed by the FMCW radar system.